2009-2012 Isuzu N Series 4HV1-CNG Engine Workshop Manual – LG4HV-WE-0981

Description

2009-2012 Isuzu N Series 4HV1-CNG Engine Workshop Manual (LG4HV-WE-0981)

This 2009-2012 Isuzu N Series 4HV1-CNG Engine Workshop Manual is the complete service and repair guide for the 4HV1-CNG compressed natural gas engine fitted to Isuzu N Series trucks. Document LG4HV-WE-0981, Sixth Edition, published November 2012, spans 326 pages of engine-specific procedures, specifications, torque values, and exploded-view illustrations. It covers NLR, NMR, and NPR models across the 2009, 2010, 2011, and 2012 model years, and it is written for the CNG engine only, not the diesel variants.

File Details

• Manual Type: Engine Workshop Manual
• Brand: Isuzu
• Model: N Series (NLR, NMR, NPR)
• Engine: 4HV1-CNG (Compressed Natural Gas)
• Coverage Years: 2009-2012
• Language: English
• Page Count: 326
• File Format: PDF
• Document Number: LG4HV-WE-0981
• Edition: Sixth Edition
• Date: November 2012
• Publisher: Isuzu Motors Limited

Chapters Covered

• 1B Engine Mechanical (4HV1-CNG)
• 1C Engine Cooling (4HV1-CNG)
• 1D Engine Fuel (4HV1-CNG)
• 1E Engine Electrical (4HV1-CNG)
• 1G Engine Exhaust (4HV1-CNG)
• 1H Engine Lubrication (4HV1-CNG)
• 1I Engine Speed Control System (4HV1-CNG)
• 1J Induction (4HV1-CNG)

Engine Mechanical (Section 1B)

The largest section of this 4HV1-CNG workshop manual covers mechanical service in exhaustive detail. Every major engine component has removal, disassembly, inspection, reassembly, and installation procedures with torque specifications and exploded-view drawings. You will find complete coverage of the cylinder head cover, intake manifold, exhaust manifold, timing gear train, valve stem seals and valve springs, rocker arm shaft assembly, camshaft, cylinder head, crankshaft position sensor, flywheel, front cover, crankshaft front and rear oil seals, piston and connecting rod, crankshaft, and cylinder block. Valve clearance inspection and adjustment is documented at the 0.4 mm (0.016 in) specification for both intake and exhaust, and the compression pressure test walks through the CNG-specific safety steps of closing the manual cylinder valve, running the engine until it stops, and then cranking for the test.

Cooling, Fuel, and Lubrication

Section 1C covers the cooling system in detail, including the water pump, the two-thermostat arrangement (82 degrees C and 85 degrees C opening temperatures), the engine coolant temperature sensor, radiator, and drive belt adjustment. Section 1D is the fuel system chapter for the CNG engine and covers the gas injector, CNG pressure and temperature sensors, pressure regulator, automatic valves, CNG container, gas filter, and filling unit, along with the rigid fuel line torque specifications. Section 1H covers the lubrication system with the oil filter cartridge, oil filter assembly, oil cooler, oil pan, oil pump, and oil pressure switch, including the 10.5 L lubricant capacity and the oil pressure specification of 340 kPa or more at 3200 r/min.

Electrical, Exhaust, Speed Control, and Induction

Section 1E covers the starting system, charging system, ignition system, knock sensor, and DC-DC converter with starter motor and generator specifications. Section 1G covers the exhaust system including the exhaust pipe, exhaust brake, air-fuel ratio sensor, O2 sensor, and magnetic valve. Section 1I covers the accelerator pedal position sensor and control link assembly. Section 1J covers the air cleaner element, IAT sensor, MAP sensor, and throttle valve.

Key Specifications Found in This Manual

• Engine type: 4HV1-CNG, 4-cycle water-cooled inline 4-cylinder
• Total displacement: 4.570 L (278.9 cu in)
• Bore x stroke: 115 x 110 mm (4.53 x 4.33 in)
• Compression ratio: 12.5
• Fuel system: Multipoint injection (MPI)
• Valve clearance: 0.4 mm (0.016 in) intake and exhaust
• Spark plug: DENSO GX8-1, gap 0.7-0.8 mm
• Coolant capacity: 12 L (2.64 Imp gal) including radiator
• Lubricant capacity: 10.5 L (2.31 Imp gal)
• No-load revolution speed: 650 r/min

CNG-Specific Safety and Service Procedures

Working on a compressed natural gas engine requires procedures that do not appear in diesel or gasoline manuals. This manual includes dedicated gas safety precautions covering the 20 MPa (204 kg/cm2/2900 psi) maximum cylinder pressure, the requirement to close all manual cylinder valves and run the engine until it stops before removing fuel system components, and the force-open procedure for the fuel shutoff valve used during leak testing. The fuel leak inspection procedure using gas leak detection fluid or soapy water at the rigid and flexible fuel line fittings is documented along with the PI monitor connector pin connections needed to force-open the valve. If you are new to CNG engine service, these procedures are essential reading before you touch the fuel system.

Gas Fuel System Components Covered

The fuel system chapter covers the full CNG path from tank to injector. You will find removal and installation procedures for the gas injector, CNG pressure sensor, CNG temperature sensor, CNG pressure and temperature sensor (combined unit on non-Australia models), pressure regulator, automatic valve before the regulator, automatic valve at the tank, CNG container, gas filter, and filling unit. The rigid fuel line couplers use a spool lock fitting with a torque method for tightening, and the manual specifies the 29 N.m (3.0 kg.m/22 lb.ft) torque for the Dia of 6.35 mm rigid fuel line coupler. For the pressure regulator, the manual documents the 0.4 MPa (4.1 kg/cm2/58 psi) output pressure that feeds the gas injectors, and the heater pipe circuit that stabilizes regulator operation.

Engine Rebuild Procedures Included

If you are doing a full rebuild, the manual walks through the complete engine disassembly sequence, starting with the engine assembly removal and continuing through the cylinder head, timing gear train, pistons and connecting rods, crankshaft, and cylinder block. Bearing selection is covered with grade tables for the crankshaft main bearings and connecting rod bearings, including the color-coded identification system and oil clearance ranges. Piston ring end gap and ring groove clearance limits are specified, along with cylinder liner protrusion measurements and the liner grade selection table (1X and 3X) that matches the cylinder block bore grade. Cylinder head flatness, valve guide clearance, valve seat contact width, and valve spring free length limits are all documented with standard values and repair limits so you can decide whether to reuse, repair, or replace each component.

Special Tools Referenced in the Manual

Throughout the procedures, special tools are called out with their Isuzu part numbers, including the crankshaft stopper (5-8840-2230-0), valve spring compressor (5-8840-2228-0), valve stem seal installer (8-9439-6815-0), scissors gear spring wrench (5-8840-2674-1), sealing cup installer (5-8840-2222-0), angle gauge (5-8840-0266-0), slinger puller (5-8840-2360-0), oil seal installer kit (5-8840-2703-0), connecting rod bushing replacer (5-8840-2340-0), crankshaft gear puller (8-9439-6818-0) and installer (8-9439-6819-0), compression gauge (5-8840-2675-0), adaptor (5-8840-2878-0), universal holder (5-8840-2862-0), and oil filter wrench (1-8522-1097-0). Having these part numbers on hand lets you gather the right tools before a rebuild or major repair.

Complete 4HV1-CNG Engine Service for Isuzu N Series Trucks

The 4HV1-CNG is a specialized natural gas engine, and generic diesel N Series manuals will not cover the gas injectors, pressure regulator, CNG container components, or the safety procedures that go with them. This workshop manual is written specifically for the 4HV1-CNG, so every procedure matches the engine you are working on. Whether you are replacing a cylinder head gasket, adjusting valve clearances, chasing down an unstable idle or hard start, overhauling the engine, or servicing the exhaust brake, the torque values, inspection limits, and step-by-step instructions are all here in one document.

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